1985 Scirocco - erratic guage readings!

[MJK 24]

I've got a weird problem with the coolant temperature and fuel guage on my 1985 Scirocco. It has happened a couple of times in the past 12 months but now it has happened three times this week.

There's two different scenarios:

1) Both guages will over read by 5-10%. If I turn on the dipped beam headlamps, the guages will read correctly but the clock goes off, and the main beam tell tale LED illuminates and the main beam will be on regardless of the position of the column switch to operate them

2) Both guages will under read by 5-10%. If I turn on the dipped beam headlamps, the guages will read correctly.

The only thing I can point out is that on the Mk2 Scirocco, the headlamps do not operate via a relay. They're switched directly from the switch.

Any ideas on where to look?

Thanks

[paintman]

Faulty earths?

[andyiley]

^^^^ What 'e said.

[steveo3002]

yeah the earths were never up to much on these cars , wont do any harm to go round clean them and replace the engine bay ones with a fatter cable

theres also a voltage stabilser on the back of the clocks ..little 3 prong thing , could swap that too

[AW10]

On the Mk 1 Golf/Scirocco if the cluster had a bad earth it would earth through the speedo cable and fry the spring for the speedo!

Another vote for an earth issue.